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Home -> Community -> Mailing Lists -> Oracle-L -> RE: control file parallel write
Hi Rahul,
'control file parallel write' waits are routine waits, not idle waits. Idle waits can be ignored entirely, but with routine waits you still need to be concerned about the average time for each wait, and whether you might perhaps be waiting too often. For example, if a database had too many control files the long average wait time for this event could alert you to that fact. Similarly, if an instance is performing too many checkpoints or log switches the number of waits for this event by processes other than CKPT would reflect that (although of course such problems would be obvious for a lot of other reasons as well).
Regards,
Steve Adams
http://www.ixora.com.au/ http://www.oreilly.com/catalog/orinternals/ http://www.christianity.net.au/
-----Original Message-----
From: Rahul [mailto:rahul_at_ratelindo.co.id]
Sent: Monday, 7 August 2000 17:33
To: 'yong321_at_yahoo.com'
Cc: 'Oracle List I'; 'Oracle List II'
Subject: RE: control file parallel write
i checked the v$session_event and indeed the process is CKPT which is the cause of these waits...
as now we know the reason of these waits... are these the one to be ignored ??
> > ----------
> > From: yong huang[SMTP:yong321_at_yahoo.com]
> > Reply To: ORACLE-L_at_fatcity.com
> > Sent: Monday, August 07, 2000 12:44 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: RE: control file parallel write
> >
> > Thank you, Steve. I should've checked your Web site before I posted.
> >
> > Indeed I find the same description at Metalink (as in Bug report
> 723987
> > although it's not a bug). It says this heartbeat makes sure the
> instance has an
> > exclusive lock on the thread. I think it's useful only in OPS. It's
> kind of a
> > waste of CPU for a single instance database.
> >
> > Oracle documentation says LGWR, DBWR, LCK0 use the rdbms ipc message
> event to
> > indicate they're idle. Why does it not say CKPT? Maybe the
> documentation has
> > not been updated. By the way, does LGWR, DBWR or LCK0 modify the
> control file
> > when they time out?
> >
> > Best regards,
> >
> > Yong Huang
> > yong321_at_yahoo.com
> >
> > --- Steve Adams <steve.adams_at_ixora.com.au> wrote:
> > > Hi Yong,
> > >
> > > In answer to a similar question, available in the question and
> answer
> > > section of my web site for 3 March 2000 I wrote, "In 8.0.5 a
> heartbeat
> > > mechanism was included in CKPT's timeout action (every 3 seconds)
to
> > > update the checkpoint progress record for the thread in the
> > > controlfile." However, the timeout being referred to here is the
> routine
> > > timeout of its 'rdbms ipc message' wait every 3 seconds, NOT the
> > > instance checkpoint timeout that is controlled by the
> > > log_checkpoint_timeout parameter. If you were to change that
> parameter
> > > to 2 you would notice a lot more than increased 'control file
> parallel
> > > write' waits. You would also notice very bad performance!
> > >
> > > Regards,
> > > Steve Adams
> > > http://www.ixora.com.au/
> > > http://www.oreilly.com/catalog/orinternals/
> > > http://www.christianity.net.au/
> > >
> > >
> > > -----Original Message-----
> > > From: yong huang [mailto:yong321_at_yahoo.com]
> > > Sent: Monday, 7 August 2000 8:34
> > > To: Multiple recipients of list ORACLE-L
> > > Subject: Re: cntrl file paralel write
> > >
> > >
> > > Rahul,
> > >
> > > The same happens to my database. It seems the CKPT process is
> touching
> > > the
> > > control file every 3 seconds, presumably because the LGWR does its
> job
> > > every 3
> > > seconds. If you change log_checkpoint_timeout to 2, you'll notice
> your
> > > control
> > > file parallel write waits for redo log writing every 2 seconds.
> > >
> > > Yong Huang
> > > yong321_at_yahoo.com
> > >
> > > you wrote:
> > >
> > > List,
> > > a new instance, just one user connected (SYS),
> > > select * from v$system_event shows that the
> > > "control file parallel write" are increasing....!!
> > > "total waits" are increasing by 10 per 30 seconds...
> > > whenever i query the v$system_event i see an
> > > increase in the time_waited,waits in this event..
> > >
> > > is this the one to ignore ?
> > >
> > > 8.1.5, AIX
> > >
> > > Rahul
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Kick off your party with Yahoo! Invites.
> > http://invites.yahoo.com/
> > --
> > Author: yong huang
> > INET: yong321_at_yahoo.com
> >
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Lists
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> --
> Author: Rahul
> INET: rahul_at_ratelindo.co.id
>> To REMOVE yourself from this mailing list, send an E-Mail message
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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